1. Field of the Invention
The present invention relates to a method of supporting power control in a communication network, said network including a plurality of network elements that perform packet forwarding, wherein each network element includes one or more ports—element ports—.
2. Description of the Related Art
In order to reduce global CO2 emissions incurred by the operation of information and communication technology (ICT), energy management of ICT infrastructures has become one of society's key objectives. In particular, reducing the energy consumption of communication networks, e.g. data centers or core networks, which may be composed of a large number of network elements, such as network switches and network routers, has become an important partial objective within the ICT scope.
On one hand, energy saving strategies deal with questions of how to forward traffic in such a way that the network elements are optimally utilized in terms of energy consumption. For example, increasing the traffic flow on a highly loaded network element is generally more suitable, since it will more likely lead to the situation where network elements that are only lightly loaded can be relieved of all traffic flow eventually. On the other hand, and usually subsequent to the calculations of the energy saving strategies, power control mechanisms act on the network elements by shutting them down and starting them up without impacting the network's functioning. Which network elements to shut down and which ones to start up is often decided separately from the energy saving strategies and requires a consistent analysis of the network state such that only those network elements are shut down that are definitely known to be not in use.
This problem shows to be very difficult because communication networks are generally characterized by complex traffic flows and dynamic interactions between peers connected to the network. As a result, the network elements' state relevant for performing packet forwarding and routing decisions may change frequently. This leads to the particular situation that a network element cannot be shut down solely based on an analysis of its own state, but the state of adjacent network elements must also be considered. Additional complexity is introduced by the fact that power state transitions may incur a certain amount of time, and during the process of starting up, packets that cannot be forwarded via a transiting network element need to be handled in a suitable way.
Apart from energy saving strategies that focus on the optimization of the utilization of network elements, e.g. the ones described in M. Baldi, Y. Ofek: “Time for a “Greener” Internet.”, in Proceedings of the IEEE International Conference on Communications Workshops, 2009, or in PCT/EP 2010/002219 (not yet published), state of the art related to power control does not provide an effective solution on how to decide consistently and uniformly which network elements must be turned on or off in exactly which situations.
On the one hand, relatively simple methods enable to shut down and start up individual network elements (e.g. described in the White Paper: “Wake on LAN Technology.”, Lieberman Software Corporation, Rev 2—Jun. 1, 2006, or in White Paper: “Magic Packet Technology. Advanced Micro Devices.”, Publication #20213, Rev: A, Amendment/0. Issue Date: November 1995). More specifically, U.S. Pat. No. 4,677,566 and U.S. Pat. No. 4,635,195 provide a centralized power control logic system that maintains a consistent view of the power state of a set of connected network elements and allow to control the power state of each connected element by turning it on or off. These contributions do, however, not consider the larger network context each network element may be part of. In summary, the above mentioned approaches can be regarded as enabling technologies that may be used by the method proposed by the present invention.
On the other hand, some power management methods also consider interactions between processing elements of the same network element (e.g. described in US 2004/0163000 A1) or a network element's wider context (e.g. described in US2009/0274070 A1), but do not define concrete methods that consistently perform power control of all the network elements in a communication network. More specifically, US 2004/0163000 A1 describes a state machine that is incorporated into the network processor of a network element (e.g. a SOHO router), which adapts the power consumption of multiple processing elements of that network processor depending on monitored utilization of each processing element and also based on interdependencies between processing elements of the same network processor. US2009/0274070 A1 describes methods to optimize power management of end and network devices attached to a communication network.